1. Field of the Invention
The present invention relates to a radiation generator for controlling the output state of radiation.
2. Description of the Related Art
An X-ray generator has an X-ray tube that generates X-rays by emitting electrons from an electron source to a target. The electron source includes a cathode to generate electrons and a grid electrode to adjust the amount of electrons. Electrons passing through the grid are accelerated and made to impinge on the target by an acceleration voltage applied between the electron source and the target.
Japanese Patent Application Laid-Open No. 2007-42516 discloses an X-ray generator that detects a current flowing through a grid to determine the degradation of an X-ray tube.
In a radiation tube represented by an X-ray tube, a cut-off voltage is applied to a grid when the output of the radiation is stopped. If the cut-off voltage is not output as desired, the output of the radiation is not always stopped. In addition, if the output of the cut-off voltage is insufficient, an extraction voltage at the output of the radiation rises higher than a predetermined value depending on a circuit configuration. As a result, an unexpected increase in the amount of electrons emitted from an electron source may damage a target. Damage to the target results in shortening the life of the radiation tube.